A MAC ID (Media Access Control address) is a unique identifier assigned to network interfaces for communication in the physical network segment. It is a string of letters and numbers, similar to a serial number, but it is not the same. The MAC ID can be found in the same location as the serial number on the device, or it can be obtained by logging into the LOM port. The serial number is also located on the back panel of the device, as well as in the About This Mac section of Mac OS X, on the hardware itself, and on some packaging and receipts.
It is used to identify and differentiate devices. The parameter settings assigned to IP addresses, such as ARP status, ICMP, telnet, secure console access, and dynamic routing can also be retrieved using the serial number.